1. Field of the Invention
The invention relates to a control apparatus for an internal combustion engine.
2. Description of Related Art
As disclosed by Japanese Patent Application Publication No. 2011-99357 (JP-2011-99357 A), a control apparatus for an internal combustion, engine that is mounted on a vehicle such as an automobile or the like is equipped with a crank position sensor that detects a crank angle of the engine. This crank position sensor is located in the vicinity of a crank rotor that is fixed to a crankshaft of the internal combustion engine. Besides, a missing tooth and a plurality of protrusions are formed on the crank rotor. Daring integral rotation of the crank rotor with the crankshaft, when the plurality of the protrusions formed on the crank rotor pass the vicinity of the crank position sensor, a crank signal is output from the sensor. Besides, when the missing tooth formed on the crank rotor passes the vicinity of the crank position sensor, a missing tooth signal is output from the sensor. The control apparatus for the internal combustion engine detects a crank angle of the internal combustion engine on the basis of a crank signal from the crank position sensor. When a missing tooth signal is output from the sensor, a deviation of the aforementioned detected crank angle from an appropriate value is corrected.
An appropriate crank angle at the time when a missing tooth signal is output from the crank position sensor is determined in advance. In consequence, when the missing tooth signal is output, it can be determined whether or not the detected crank angle is deviant from the appropriate value. If the detected crank angle is deviant from the appropriate value, it can be corrected to the appropriate value. The cause of the deviation of the detected crank angle from the appropriate value includes a case where noise is generated in a signal output from the crank position sensor and the noise is erroneously recognized as a crank signal, a case where noise is generated in a signal output from the crank position sensor and a crank signal cannot be appropriately recognized due to the noise, and the like.
There is known an internal combustion engine that is mounted on a vehicle such as an automobile or the like and is automatically stopped and automatically restarted up during idle operation with a view to improving fuel economy. This automatic stop of the internal combustion engine is carried out by stopping fuel injection from fuel injection valves in the engine in the case where there is no request for the traveling of the automobile during idle operation of the engine, etc. Besides, automatic restart-up of the internal combustion engine in an automatically stopped state is carried out upon the fulfillment of an automatic restart-up condition, for example, when the automobile may travel. More specifically, fuel injection from the fuel injection valves is begun while cranking the internal combustion, engine. Fuel injected from the fuel injection valves is sucked into cylinders (combustion chambers) together with air in an intake passage, and is ignited by ignition plugs in a state of being mixed with air in the cylinders. Then, the fuel thus ignited burns, whereby autonomous operation of the internal combustion engine is begun to complete automatic restart-up of the engine.
It is preferable that automatic restart-up of the internal combustion engine in an automatically stopped state be swiftly completed after the beginning of cranking for automatic restart-up. In order to realize this, it is important to appropriately supply fuel to the cylinder in which a piston is stopped in an intake stroke, among the respective cylinders of the internal combustion engine in an automatically stopped state, after the beginning of automatic restart-up, accurately ignite the fuel in an initial compression stroke, and thereby make a combustion process of the fuel favorable. Incidentally, in the control apparatus for the internal combustion engine, which is automatically stopped and automatically restarted up, the detected crank angle is held during automatic stop as well. Therefore, fuel injection and ignition after the beginning of automatic restart-up can be carried out on the basis of the crank angle.
However, during automatic stop of the internal combustion engine as well, the detected crank angle may deviate from an appropriate value as a result of the generation of noise in a signal that is output from the crank position sensor. If the crank angle thus deviates from the appropriate value, ignition after the beginning of automatic restart-up of the internal combustion engine cannot be carried out at an appropriate timing. Furthermore, such a deviation may hinder efforts to make the initial combustion process of fuel after the beginning of automatic restart-up favorable. In order to cope with this problem, the following method is conceivable. That is, initial ignition after the beginning of automatic restart-up is carried out after a missing tooth signal is output from the crank position sensor after the beginning of automatic restart-up, more specifically, after the deviation of the aforementioned detected crank angle from the appropriate value is corrected on the basis of the outputting of the missing tooth signal. In this case, initial ignition after, the beginning of automatic restart-up is not carried out on the basis of the detected crank angle, with the crank angle deviant from the appropriate value. Therefore, the occurrence of the aforementioned problem can be avoided.
As described above, in automatically restarting up the internal combustion engine which is in an automatically stopped state, if initial ignition after the beginning of automatic restart-up is carried out on the basis of the crank angle, after a missing tooth, signal is output from the crank, position sensor and the crank angle is corrected, the combustion process of fuel based on the initial ignition can be made favorable. However, a missing tooth signal may not be output from the crank position sensor immediately after the beginning of automatic restart-up of the internal combustion engine which is in an automatically stopped state. Accordingly, the outputting of the missing tooth signal may be delayed if the crank angle of the internal combustion engine which is in, an automatically stopped state assumes a certain value. In the case where the outputting of the aforementioned missing tooth signal after the beginning of automatic restart-up is thus delayed, the completion of automatic restart-up of the internal combustion engine is delayed correspondingly.